Compact wide stopband lowpass filter using spiral loaded tapered compact microstrip resonator cell

A new spiral loaded tapered compact microstrip resonator cell (SPLT-CMRC) is presented. The addition of spiral stubs to the CMRC creates transmission zeroes in the stopband which extended the stopband of the lter. The proposed resonator is used to design a compact lowpass lter (LPF) with wide and high rejection in stopband. The fabricated lter has a 3 dB cutoff frequency at 8 GHz. The insertion loss in the passband is less than 0.2 dB from DC to 7.2 GHz. The proposed lter has wide stopband from 9.47 to 40 GHz with attenuation level of -20 dB. The demonstrated filter is designed and fabricated. There is a good agreement between the measured and simulated S-parameters. © 2013 Taylor & Francis.